|
D2 - Fuel and Exhausts Everything to do with getting fuel into the engine, and fumes back out again |
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Nct emmisions fail
Hi all.
My1996 4.2 v8 a8 fail the nct/mot today on its emmisions.. Again... It failed previously on this and the exhaust was leaking so had part of it replaced and now the readings are even higher. Shockingly high. Now it'll be going back to the garage next week but I suppose I'm just looking for ideas... Readings are below. These are today's readings. Low idle: Co 6.63 vol above 0.50 %fail Hc 234ppm High idle lambda 0.82. Not between 0.97 and 1.03 Co 6.63 above 0.30%. Fail Hc234 ppm. Above 200ppm fail Any ideas? Thanks |
#2
|
||||
|
||||
Just for info, my car recently passed the MOT test (facelift edition, model year 2000 A8L) with the following figures:
HC (limit 200) - reading was 46 ppm vol Lambda (limit 0.97-1.03) - reading was 1.006
__________________
2010 B8 S5 Sportback quattro 3.0 Supercharged in Sprint Blue (current girlfriend) 2000 D2 A8L quattro 4.2 in Audi silver (my ex-girlfriend) |
#3
|
|||
|
|||
That's running quite rich. Any fault codes stored in ECU? My guess would be there is an air leak in exhaust system not far from lambdas letting fresh air in, lambdas read it as lean and ECU then chucks in too much fuel.
__________________
Currently 8less 2011 Q7 S Line 3.0TDI, 2016 Tesla Model S 90D 8 history: 2006 A8 Sport 4.2TDI quattro SOLD, 1997 S8, reached end of life with gearbox failure |
#4
|
|||
|
|||
I was told that there's no codes in the ecu, and they welded in new pipe before the cats... Hopefully they've made a mess of it and that it's just that... Fingers crossed but your right does sound like it's running super rich...
|
#5
|
|||
|
|||
Could also be the lambda sensors reading lean so the ecu is over-fuelling. Try unplugging them as a diagnostic step as the ECU will just run open-loop using the MAF. If it improves the reading then replace the sensors. If not, look elsewhere
|
#6
|
|||
|
|||
Great thats a start... Will try that 1st....
Thank you. |
#7
|
|||
|
|||
Just following up here. Have replaced left bank o2 sensor as it seemed dead according to the diagnostic in the garage and after a smoke test 2 breather pipes from the inlet manifold were split open.
After that the emmisions in the garage recorded fine, so nct retest Tuesday... Fingers crossed. |
#8
|
|||
|
|||
Passed retest... Was the above. Whoop whoop!
|
|
|